Thamnobryum Nieuwland, 1917.

Thamnobryum (with Climacium and Leucolepis) is one of our three truly dendroid mosses. In California, it seems almost restricted to soil in high montane coniferous forests, and in high elevation Alnus thickets. A quick hand-lens look at the leaves of this plant is sufficient for identification: blunt leaves, no limbidium, short cells of the median lamina.
see key to Neckera Etc.